1. Technical Field
The disclosure relates to a variable valve mechanism used for a valve system or the like of an engine, for example, and particularly, relates to a cam-switching variable valve mechanism in which any one of a plurality of cams is selected by sliding a cam unit in an axial direction (a cam axial direction), the cam unit being provided around a camshaft.
2. Description of Related Art
Conventionally, as a variable valve mechanism that can change a lift characteristic of an intake valve or an exhaust valve of an engine, a Variable Valve Timing (VVT) that can continuously change a valve timing is used widely. Further, as described in Japanese Patent Application Publication No. 2010-520395 (JP 2010-520395 A), for example, there has been publicly known a cam-switching variable valve mechanism in which a cam carrier (a cam unit) provided with a plurality of cams is provided around a camshaft, and any one of the cams is selected by sliding the cam carrier in an axial direction of the camshaft.
In the variable valve mechanism according to the conventional example, a spiral guide groove is provided on an outer periphery of the cam carrier, and an engagement element (hereinafter referred to as a shift pin) of a servo-mechanism is engaged with the guide groove from the outside. In the configuration, when the cam carrier rotates integrally with the camshaft, the shift pin relatively moves along the guide groove. This practically maintains the engagement between the guide groove and the shift pin, and thus, the cam carrier slides in the cam axial direction.
More specifically, as illustrated in FIG. 8, a guide groove G in the conventional example is configured in a Y-shape as a whole such that an S-shaped groove g1 and a reverse S-shaped groove g2 formed on an outer periphery of a cam carrier C so as to extend in a circumferential direction are joined to each other. When the cam carrier C is moved toward a left side in FIG. 8, the shift pin P is inserted into the S-shaped groove g1, and the shift pin P is relatively moved along the groove g1 toward a right side in FIG. 8.